Coats of Arms were awarded to an individual not to people with the same surname. these Coats of Arms were able to be passed from the person awarded this to the elder son and so on down the line. it did not mean that cousins, and everyone of the surname is or was entitled to use those Coats of Arms. If no elder son to inherit then the Coat of Arms became extinct.
The elder son upon inheritanc would have to apply to the College of Arms to have the matter ratified.